642MX

goalpostcasualty

No the guy I bought the bike from ruined the manual... or so he said. But I was just checking. I recently had a post on here and I was having problems all of a sudden on how it was running. One day I was riding and it ran like a champ and the next day it was popping and backfiring when I would get on the gas and when I would get off the gas. So I cleaned the carb, jets, etc right and it still didn't help... So I changed the plug out but couldn't get a NGK so I bought a Autolite instead. It ran fine the next time I took it out. I rode it for probably 1.5 to 2 hours and then put it up thinking everything was fine. Ok its been 3 days since and I went to ride it today and it cranks fine and idles fine but when I get on the gas it backfires again! NO FREAKIN IDEA WHATS GOING ON! It couldnt have fouled the plug that quick could it? If you want the whole story look up "YZ450 REVVING PROBLEMS". Thats my post. Any ideas on how to fix it or what might be the problem?